High-end Pentium® 4-based products (all Xeon MPs, later model Xeon DPs, Pentium® 4 Extreme Edition) incorporate an on-die L3 Cache. It has the following major characteristics:
It is a unified cache (i.e., it caches both code and data and does not discriminate between the two).
It is physically-addressed and physically-tagged.
512KB, 1MB, 2MB or 4MB in size.
It is an 8-way set-associative cache.
It is a Write-Back (MESI) cache.
The cache line size is 128 bytes, with each line divided into 64 byte sectors.
It is a non-blocking cache.
It can cache from the full 64GB physical memory space.
ECC-protected. It can detect and correct single-bit failures and detect (but not correct) multi-bit failures.